The present invention addresses a number of problems associated with the growth of living organisms in or about various types of fixed facilities. A typical example of such a facility would be an industrial plant in which water is circulated through a heat exchanger, cooled by passing the water through a cooling tower, and then recirculated back to the heat exchanger. Microorganisms such as bacteria, etc., can grow in the water, in the cooling tower, in the various pipes connecting those and other items to form a water flow circuit, and in some cases, in the heat exchanger. These microorganisms can create health hazards, unpleasant odors, and various other well-known types of problems. In addition, some such organisms build up considerable solid matter, such as slime and algal deposits, that can cause a host of other types of problems, such as clogged lines, slippery and dangerous surfaces, undesired insulation that interferes with proper heat transfer, etc.
Another example of a type of facility in which living organisms can create problems would be a plant that draws cooling water from a nearby natural body of water, man-made lake, or the like and/or re-injects hot water back into that body. In certain parts of North America, for example, the populations of certain non-native species of mollusks, which have been accidently introduced into North American waters via foreign vessels or the like, have, in the absence of their native predators, exploded, so that these mollusks have become pests. Some of them are quite small, and can enter into and clog the lines through which the water is taken from, or re-injected into, the body of water, and can even be carried further into the plant with the water stream, thereby causing problems.
Accordingly, there are a number of different types of facilities in which it is desirable to be able to kill and eliminate such organisms, in as safe and trouble-free a manner as possible, and preferably without the need to shut down the normal operation of the facility.
Current systems and methods for addressing these problems leave much to be desired.
Probably the most common substance currently used in the treatment of heat exchangers, cooling towers, and like facilities in industrial plants is chlorine gas. Because this biocide is used in a gaseous form, it is necessary to have large quantities available for treatment, and this gas is typically stored in large containers at the site of the facility whose treatment will be required. As is well known, chlorine gas is very dangerous. Therefore, fairly onerous safety precautions are necessary. It is usually necessary to obtain special permits for the storage and use of this gas, and complying with the requirement to obtain such permits can be burdensome. Specially trained operators are typically kept on the staff of the facility using the chlorine gas for biocide treatment.
Chlorine dioxide is an even better biocide than chlorine gas. It can even clean high efficiency PVC fill, which is sometimes used in cooling towers. However, in gaseous form, it is even more dangerous than chlorine gas. Furthermore, various precursors or reagents from which chlorine dioxide can be formed are dangerous or harmful. These include (depending on the process) chlorine gas itself, sodium chlorate, sodium chlorite, sodium hypochlorite, and/or strong acids. Though the sodium chlorite is used in a liquid solution, which is therefore easier than gas to contain or recapture if it is spilled, once it is spilled and dries, it leaves a very problematic residue that is highly flammable in conjunction with organics.
There have been some efforts in the past to provide chlorine dioxide dissolved in a carrier liquid such as water, for purposes of cleaning up petroleum spills and/or residues, e.g. around oil fields. It is believed that, in at least one such instance, it was attempted to provide a chlorine dioxide generator, along with all necessary materials, in a portable system, e.g. chemicals, generator, etc., on a "goose neck" trailer on one truck, and water on another truck. This system was limited to small applications, and even then, employed a large, unwieldy system, with various potential safety problems. It was not suitable for industrial plants.
Another portable system, using sodium chlorate as a precursor, is believed to have been offered, likewise, for use in oil field applications. It was likewise unsuitable for industrial plants, and apparently unsuccessful even in the oil field.
Accordingly, the general tendency has been to avoid the use of chlorine dioxide for biocidal treatment of fixed facilities such as plants.